Low pressure developing today off the mid-Atlantic coast will ride up the Eastern Seaboard tonight and tomorrow, rapidly strengthening as it does so. This low will undergo cyclongenesis (maybe even bombogenesis) as tracks north past Cape Cod and Boston tomorrow, eventually tracking into Maine tomorrow afternoon. This low will spread heavy rain and very high elevation snow over New England tomorrow morning into tomorrow afternoon before cold air works in and starts to lower the snow levels. By tomorrow afternoon/night as strong northwest winds pick up in response to the deepening surface low, precipitation will become focused over the upslope regions of the northern Adirondacks, central and northern Greens, and northern Whites. Friday Night and Saturday should produce very significant snow over these upslope favored areas where accumulations could be measured in feet by Saturday Night.

During the first half of this storm (late tonight into Friday afternoon) when the most widespread precipitation will occur, snow levels will remain very high at 3,000ft+ in Vermont and New Hampshire. Back across the Adirondacks, snow levels will be lower but there won’t be much precipitation as the best forcing passes east of NY closer to the coastal low. By Friday afternoon and evening though the surface low gets captured by the upper level trough and actually tracks back northwestward through ME. As this low backs westward a bit in ME on Friday evening/night, it will throw Atlantic moisture back into the northern Adirondacks, central and northern Greens, and northwestern Whites. This moisture transport coupled with lowering snow levels and strong NW winds will set the stage for what appears to be a potentially memorable upslope snow event.

I’m going to start out by saying resorts favored in a North Country upslope snow event include Whiteface in the Adirondacks; Jay Peak, Smugglers Notch, Stowe, Bolton, MRG, and Sugarbush in Green Mountains; and Cannon, Bretton Woods, and Wildcat in the White Mountains. These mountains are at the highest risk of receiving significant snowfall out of this phase of the storm and are the areas I am focusing on primarily for this forecast. There could certainly be some light to moderate accumulations south of these resorts (generally 6” or less) but it will be negligible compared to what could transpire across the northern mountains.
From 00z SAT (7pm Friday EST) to after 18z (1PM EST) SAT these areas are absolutely ravaged by H85 (~4,500-5,000ft) winds of 40-60kts out of the NW. This is 60mph gusts on the ridge-tops at 4,000ft for one thing but in terms of upslope snow this strong NW wind is very important. For a little education on upslope snow, here are the main criteria I look for. These criteria are based on CSTAR research on upslope snow events in the northern Adirondacks and central/northern Greens:

1) Moist profile of RH>90% from near the surface to 850mb (near or just above ridge-top height).
2) NW wind flow at H85 of >25kts with signficant cross-barrier component (wind direction of 270-320 degrees)
3) For a big event, the duration of NW flow into the upslope region needs to be >12hrs.

For this event we exceed all three of those criteria… the moist cyclonic flow around the vertically stacked low pressure system keeps us moist in the low levels, NW winds at H85 rip at 40-55kts (in my experience, the big events occur with winds higher than 40kts at H85), and the duration of these winds/moisture combo appear to last for up to 18 or more hours. Looking at the BTV soundings for 12z/7am Saturday shows sufficient low level moisture and the wind fields could not look any better. It’s a textbook NW cyclonic flow and due to the vertical stacking of the surface low, mid level low, and upper level low, winds at all levels of the atmosphere are uniform, and strong out of the NW.

The only negative to consider here is snow growth. For really big upslope we want to see the favorable -12C to -18C temps in the H85-H7 region where the best lift generally occurs. Temps in this layer are progged to be less than stellar which is a concern for efficient snowflake production. I have no doubt that the upslope process of forced ascent of the parcel will be very efficient in producing significant precipitation but snow ratios should stay close to 10-12:1. Based on the temperature between the H85 and H7 levels, I fear flake type could be a lot of needles so it could be denser than normal upslope. Still, with the local WRF 4km-grid model (run out of the NWS WFO BTV) showing generally 1-2” of QPF across the central and northern Green Mountain spine, northern slopes of the Adirondacks, and northwestern Whites, this should be a significant upper elevation snowstorm.

Upslope snow is fairly elevation dependent to begin with, as the heaviest precipitation occurs over the immediate peaks, but temperatures will be marginal below 2,000ft so this could be more elevation dependent than normal. As far as Storm Totals go, here is what I am thinking for this long-duration event starting Friday 7am and ending Saturday 10pm. I’ll admit I am not as familiar with upslope snow events in the White Mountains but do believe that the northern slope of the Presidential Range from Gorham to Franconia Notch will make out quite nicely from this event. I’m forecasting them to receive a little less than their Green Mountain neighbors but they should still get a sizable snowfall. The lower end of these ranges might be closer to reality but I know how efficient these upslope events can be (and all signs point to a big event) so I feel comfortable forecasting a high upper value.

Northern Adirondacks including Whiteface… 6-12”

Northern Greens including Jay Peak, Smuggs, Stowe, Bolton… 12-24” above 2,000ft…4-12” from 1,000ft-2,000ft.

North-Central Greens including Mad River Glen and Sugarbush… 10-18” above 2,000ft… 4-10” from 1,000ft-2,000ft.

Central Greens including Killington…6-12” above 2,000ft, 2-6” from 1,000-2,000ft.

Southern Green Mountains including everyone between Okemo and Mt Snow…2-5” above 2,000ft, trace-2” below that.

Northern Whites including Cannon, Bretton Woods, and Wildcat…8-16” above 2,000ft and 4-8” from 1,000-2,000ft.

Central and southern Whites including Attitash, Waterville Valley, and Loon…4-8” above 2,000ft, 1-4” between 1,000-2,000ft.


  1. werw
    wrote on November 26th, 2009 at 2:48 pm  
  2. MadPatSki
    wrote on November 26th, 2009 at 3:56 pm  
  3. Greg
    wrote on November 26th, 2009 at 4:00 pm  

    The board is set…. the pieces are moving

    • MadPatSkl
      wrote on November 26th, 2009 at 11:25 pm  

      Where are you moving your pieces? I just need to check (stuff) mate!!!

    • Greg
      wrote on November 27th, 2009 at 11:42 am  

      Probably Stowe.

  4. Scott
    wrote on November 26th, 2009 at 4:37 pm  

    I’d just like to add the updated NWS forecast for Mt. Mansfield (Stowe)…looks like the NWS is on-board for significant mountain snow. They have 11-19″ of snow forecast by Saturday morning with more falling during the day on Saturday in upslope snow showers:

    Friday: Snow. High near 33. North wind 5 to 8 mph increasing to between 13 and 16 mph. Chance of precipitation is 100%. New snow accumulation of 6 to 10 inches possible.

    Friday Night: Snow. Low around 23. Blustery, with a north wind between 18 and 25 mph. Chance of precipitation is 100%. New snow accumulation of 5 to 9 inches possible.

    Saturday: Snow showers likely, mainly before 1pm. Cloudy, with a high near 24. Windy, with a northwest wind between 22 and 30 mph. Chance of precipitation is 60%.

  5. Burke
    wrote on November 26th, 2009 at 7:38 pm  

    You forgot to mention Burke Mountain!!! (between the greens and the whites!)

  6. Mitch
    wrote on November 26th, 2009 at 8:05 pm  

    Nice! in my experience with upslope events i’ve seen some parts of southern vermont can really cash in as well, especially near woodford state park. Its no comparison to what your going to get up north though! That being said, i wouldnt be suprised to see an 8 inch lollipop from a spotter above 2k feet in the southern greens.

    • Scott
      wrote on November 26th, 2009 at 8:35 pm  

      Mitch… yes, this is true. There is a spotter there at like 2,400ft on Woodford Mountain that always cashes in. I could certainly see a 6-8″ total coming from the high country near there just based on the high elevation near Woodford State Park.

  7. billski
    wrote on November 26th, 2009 at 10:11 pm  

    Hit me with your best shot, fire away!!!!

  8. tylerjames
    wrote on November 27th, 2009 at 12:49 am  
  9. Josh
    wrote on November 27th, 2009 at 9:55 am  

    Hey Scott, just noticed the NWS downgraded their snow total prediction for Mansfield this morning. Do you agree with this? Any significant changes to your above guesses? Thanks.

    • Scott
      wrote on November 27th, 2009 at 11:24 am  

      I’m not concerned…the NWS forecast has a tendency to jump around quite a bit with every update on the point and click forecast. I think that the highest realistically achievable snowfall amount might be only 18″ up top instead of 24″…but I’m still thinking over a foot above 2,000ft for the northern spine.

      I actually think the cut-off gradient between significant snow and almost no snow is going to be very tight around 1,500ft.

      This should be a fun event of rain changing to snow and high winds across the mountains. Its a heck of a lot better than the rest of November and this heavy wet snow will lay down a nice base.

  10. rocoJerry
    wrote on November 27th, 2009 at 2:53 pm  

    Do you think the last few inches of this storm will be heavy/wet snow?

    • Greg
      wrote on November 27th, 2009 at 3:17 pm  

      Depends where you are talking about. North of rt 2 the final snow will fall off a stiff nnw wind upsloping over the greens. You can expect that to be dry although due to temps in the mid 20s snow quality may be needles which are denser than large dendrite flakes. Further siuth the only snow will be from the low pressure itself most of which will fall as wet flakes. That is my understanding at least. Scott?

    • Scott
      wrote on November 27th, 2009 at 3:45 pm  

      Yeah. I’d expect the last few inches in the northern mountains to be of the drier type but not by much. This will primarily be a heavy, caking snow as there really isn’t much cold air to wrap into this system. I’m starting to think I’m too high on snow accums below 2,000ft as its still pretty warm (ie. 36F at 1,640ft at the base of Stowe) and ratios are going to be awful below 2K feet (like 6-8:1). However, the Stowe cam is showing snow above 2,000ft right now with the trails are now white on the upper half of the mountain. What happens between now and say 7am tomorrow makes or breaks this storm!

  11. AJ Kappe
    wrote on November 27th, 2009 at 5:05 pm  

    Any white is white enough for this storm to be, “Made” for me. So far webcams show good things. Tela and I will see you guys on the slopes.

    What phone # do I call for my “Good morning skiers and riders”??

  12. Nic
    wrote on November 27th, 2009 at 5:51 pm  

    I like this. Looking forward to skiing tomorrow

  13. Kyle
    wrote on November 27th, 2009 at 10:24 pm  

    Cannon is reporting 8 inches at the top…How much additional snow can they expect?

  14. Scott
    wrote on November 28th, 2009 at 8:54 am  

    Storm was about 3-4F warmer throughout the column than expected… this is very elevation dependent and very wet, heavy snow. Skiing will be done today but this storm wasn’t quite the juggernaut it was looking to be; we had the precip and wind, it just wasn’t cold enough.

  15. monkfish
    wrote on November 28th, 2009 at 11:08 am  

    I aspire merely to be an amateur met myself, but … judging from radar it looks to me like the low wound up hugging the ME coast rather than turning inland, and axis of max upslope shifted east. N NH bullseye? I collected these reports from Twitter & websites:

    Stowe 6-18 with 12 at the stake; Smuggs 10-12 up top; Jay 7-8 at base and snowing heavily as of 7:15 a.m. (NWS spotter reported 10.0 on Rte 105 at 5:48 a.m.); Killington 10″ wet snow up top; Bretton Woods 14-18; nothing this a.m. from Cannon but at 6p yesterday they said 4 at base, 2x that at summit; SR 6-8 atop Locke; ‘Loaf 8 at base, more up top.

  16. Joann
    wrote on November 29th, 2009 at 10:18 am  

    Hey guys,
    Nice Stowe shots.
    FYI on your beautiful weather tool page….your web cam labeled, “Keene” really is the base lodge at Whiteface Mountain, between Lake Placid and Wilmington, New York. Hope to see you there sometime!

    • Greg
      wrote on December 1st, 2009 at 2:37 pm  

      Thanks Joann. I’ll fix that soon!

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